The present invention relates to rotary devices such as pumps, compressors and the like and more particularly to a unique thermally compensated seal which increases the efficiency of such devices.
The efficiency of rotary devices utilized for pumping a fluid or compressing a vapor largely depends upon the internal tolerances of the components comprising the device. A loosely-toleranced rotary pump or compressor may have a relatively poor fit between internal components and may therefore exhibit poor efficiency, with relatively high leakage occurring within the device from regions of high pressure to regions of lower pressure. The traditional approach to this situation is to decrease the amount of clearance on these critical interfaces. This approach in turn dictates tighter tolerances for the individual components and requires more expensive manufacturing processes. For example, it may be possible to generate a 1.000".+-.0.001" dimension by machining on a lathe, but a 1.0000".+-.0.0002" dimension will require secondary machining operations such as grinding or lapping. Thus, it has traditionally been relatively expensive to create a compressor or pump with minimal clearances and high efficiency.
An alternate solution to the leakage problem uses an elastomeric seal to close the gap. O-rings or lip type seals can be used in many instances to seal very effectively. This approach is widely used to seal against rotating shafts, for instance. Where there is relative motion against an interrupted surface, however, elastomeric seals will suffer accelerated wear and premature failure. For this reason traditional elastomeric seals are not a good sealing means for the gap between time rotor and covers of a rotary vane compressor or motor.